This invention relates to improvements in large size vessels for the stationary storage of fuel oil and other liquids, and more particularly to large size rigid tanks provided with means for the accumulation and removal of sludge or other sedimentary impurities associated with liquids confined therein.
Liquid hydrocarbon fuels such as gasoline, kerosine, and heating oils such as bunker #2, have a tendency to form gel particles in the course of aging due to polymerization phenomena accelerated by residues of cracking catalysts. Such particles have an adverse affect on equipment intended for the utilization of the fuels, causing clogging of burner orifices or build-up on moving parts of control systems. Screen and strainer filters of various kinds have been disclosed for the removal of suspended impurities, but they are all of limited effectiveness because the particles fill the pores of the filter, necessitating frequent attention to prevent interruption of the flow of fuel. In stationary systems which permit quiescent storage, the particles eventually settle to the bottom of the confining vessel to form a sludge.
It has long been sought to devise methods and apparatus whereby sludge can be removed from storage vessels. However, this has proven to be a difficult accomplishment particularly because of the inaccessibility of the interior of storage vessels during use, and the fact that the vessels are generally of cylindrical configuration and horizontally disposed with respect to their longitudinal axis, causing a layer of sludge to traverse the entire lower portion of the vessel. Accessibility to the interior bottom portion of storage vessels is even more difficult when said vessels are located underground, as is the general case. The term "large size" as employed herein in intended to denote vessels having a volumetric capacity of between about 275 and 1,000 gallons.
Various designs have been proposed for small gasoline tanks utilized in automotive vehicles to facilitate sludge removal. Typical of such designs are those disclosed in U.S. Pat. Nos. 1,235,438; 2,339,303; 1,063,754; 1,792,827; 2,001,610; and 1,055,744. Said patents in general describe tanks having depressions or wells in their underside portion to cause accumulation of sedimentary material. However, the apparatus and techniques utilized for finally separating the collected impurities from the fuel are not amenable to practical use in the case of large stationary tanks.
It is accordingly an object of the present invention to provide a large vessel for the stationary storage of liquids and provided with means for the accumulation and removal of sedimentary material. It is another object of the present invention to provide a large vessel for the stationary storage of hydrocarbon liquids and provided with means involving no moving parts for the accumulation and removal of sedimentary material. It is a still further object of this invention to provide a large vessel of the aforesaid nature of simple and durable construction capable of easy installation and simple operational use. These objects and other objects and advantages of the invention will be apparent from the following description.